Ex 2- Virus Classification, Structure, & Replication- Middleton Flashcards
1
Q
What is the difference btw virus and bacterium?
A
- bacteria replicate on own
- virus require host to replicate
2
Q
What is the difference btw a virus and a toxin?
A
- virus can replicate w/ host
- toxin cannot replicate
3
Q
_____ and _____ disease was the first animal virus discovered
A
foot and mouth
4
Q
______ _____ virus was the first human virus discovered in 1901
A
yellow fever
5
Q
Viruses are _____ than bacteria, fungus, and other microorganisms
A
smaller
6
Q
Viruses replicate when provided a _______
A
host
7
Q
Viruses are obligate intracellular ______ and not autopoietic
A
parasites
8
Q
virus means “_____” in Greek
A
poision
9
Q
Viruses are _______ to nature and don’t always cause disease
A
ubiquitious
10
Q
What are the 2 theories of virus origin?
A
- cellular
- autopoietic
11
Q
The ______ origin theory proposes that viruses were once cellular components but over time they evolved separately
A
cellular
12
Q
The _____ origin theory proposes that viruses, once autopoietic entities, became dependent on cells for replication
A
autopoietic
13
Q
What attributes are used for virus classification?
A
- particle structure
- genome
- replication features
- serology (antibodies)
- stability (heat, chemicals)
14
Q
Virus particles can be classified by what 3 things?
A
- composition
- shape
- size
15
Q
_______ is RNA or DNA in a core that is protected by a protein coat (capsid)
A
nucleocapsid
16
Q
A virus can be defined by the ________ structure
A
nucleocapsid
17
Q
What are three types of nucleocapsid structures based on symmetry?
A
- helical
- pleomorphic
- icosahedral
18
Q
A nucleocapsid is comprised of repeating protein subunits (1,2 or 3)called ________
A
capsomeres
19
Q
________ are virus-modified cellular membranes acquired upon exit from host
A
envelopes
20
Q
Exposure to _____ solvents renders enveloped viruses noninfectious
A
lipid (ie alcohol, ether,acetone, Freon, etc)
21
Q
Enveloped viruses may have ______ with different structures
A
nucleocapsids
22
Q
____ nm is the smallest virus particle and _____ nm is the largest virus particle
A
- 18 nm
- 300 nm (almost size of bacteria)
23
Q
What are the advantages of having a small size?
A
- small genomes can replicate quicker
24
Q
What are the advantages of having a large size?
A
- large genomes carry more genes + proteins (immune modulators) that downregulate innate immunity
25
What are the different compositions of a viral genome?
double or single stranded DNA or RNA
26
What are the different types of single stranded RNA?
(+)ssRNA
(-)ssRNA
Ambisense
27
(__) ssRNA can be used directly for the translation of proteins
(+)
28
(__) ssRNA has to make (__) sense copy to replicate
(-)
| +
29
____ ssRNA has portions that are minus and plus sense
ambisense
30
What are the different structures (gene arrangements) of the viral genome?
- linear
- circular
- segmented
- dipoloid
31
Why do viruses do not have to follow the central dogma of DNA-RNA-protein?
Reverse transcriptase which allows reverse transcription (RNA to DNA)
32
What is required for replication of a virus to begin?
ssDNA hairpin, signals for cellular machinery to copy
33
Herpesvirus requires ____ _____ ____ to initiate replication
dsDNA rolling circle
34
Picornavirus is a ( )ssRNA that sits on ribosomes and starts replication
(+)ssRNA
35
(-)ssRNA needs ____ dependent ___ plymerase to replicate
RNA
| RNA
36
What do DNA viruses needed to replicate?
nucleus- needs host cell machinery
37
RNA viruses need ____ _______ ______ ____ to replicate
RNA dependent RNA polymerase
38
What are the 7 steps to virus replication?
- attachment
- entry
- transcription
- translation
- replication
- assembly
- release
39
How do viruses attach to a cell?
binding or virus receptor to cellular receptor (our functional cells) bc cells do not have virus receptors
40
What type of cell receptors do viruses bind to?
- signaling molecules
- cell adhesion
- transport
41
How do viral receptors attach to cell receptor?
- spike like projections on particle surface
| - may require co-receptor
42
______ is a major determinant of virus tropism (host range)
Attachment
43
Viruses infect essentially ___ known forms of life
all
44
______ is the term for viruses that can infect humans and animals, which are not shared across more divergent hosts
zoonosis
45
_____ _____ is a major factor in eradication
host range
46
Viruses do not cross ______
kingdoms
47
What are the 2 pathways of viral entry?
- receptor mediated endocytosis
| - direct penetration of plasma membrane
48
What are the pathways that non-enveloped viruses enter the cell?
- pores (picornavirus)
| - membrane disruption (adenovirus, reovirus)
49
What are the pathways that enveloped viruses enter the cell?
- membrane fusion
| - receptor conformational change (pH, receptor induced)
50
What happens during nuclear replication?
- genome and remaining protein coat (nucleocapsid) transported to nuclear membrane and deliver the genome to the nucleus
51
What happens during cytoplasmic replication?
- genome released in cytoplasm and transported to intracellular site of replication
52
May RNA viruses replicate in _______ _______ complexes
membrane associated
53
dsRNA viruses never release their______ _____ from the entering particle
-genomic material, bc would cause signaling for innate immune system
54
Transcription results in the production of ______ templates for protein synthesis
mRNA
55
DNA viruses rely upon cellular _____ polymerases for transcription
RNA
56
The genome of (__)ssRNA viruses can serve as mRNA
(+)
57
( _) ssRNA and dsRNA viruses must bring in their own _____ into the cell
- (-)
| - polymerases
58
ALL viruses need the cell's _____ to produce protein bc they do not have them
ribosomes
59
Viral protein production can be regulated at the ________ level or _____ level
- transcript (mRNA)
| - translation
60
Structural proteins are produced in _____ quantities and non-structural proteins are only seen ____ the infected cell
- high
| - inside
61
The objective of virus ______ is to make additional genome copies
replication
62
The order of genomic replication of viruses depends on virus ______
genome
63
(+)ssRNA polymerase makes (__)ssRNA copy as template for new genomes
(-)
64
(__) ssRNA genomes replicate through full-length (__)ssRNA intermediate
(-)
| +
65
_____ induces innate immune response so genome stays inside particle which has viral polymerase
dsRNA
66
The mRNA of dsRNA is synthesized in the _____ and exported to the ______
- particle
| - cytoplasm
67
ssDNA and dsDNA must gain access to the _____
nucleus
68
_____ are a nexception bc the virion contains necessary info (RNA polymerase and genome encodes DNA polymerase for replication) to replicate in the cytoplasm
poxvirus
69
During viral ______ new genomes are packaged into functional particles
assembly
70
______ ______ proteins aid in assembly and the genome contains packaging signals
localized structural
71
What is the mechanism for assembly in adenovirus?
- empty protein coat imports genome
72
What is the mechanism for assembly in a reovirus?
RNA packaged during capsid assembly
73
What is the mechanism for assembly in a reterovirus?
preassembly on membrane
74
What are the different types of viral releases?
- lysis
- weak lysis
- budding (enveloped only)
75
____ is best known for bateriophage and is when viral molecules rupture the cellular membrane
lysis
76
What is the disadvantage of lysis?
viral particles released trigger immune response
77
What is a disadvantage of targeting viral replication in the nucleus?
must cross 2 membranes
78
During a ____ step growth curve viruses infect every cell at the same time and every cell dies at the end of infection
one
79
What are the 3 kinetic phases of virus replication?
- eclipse; attachment and uptake
- exponential growth; replication and assembly
- plateau; cell death bc no nucletoides or AA, exhausted resources
80
What is the length of time from the start of infection to beginning of plateau in bacteriophage, vesicular stomatitis virus, and vaccinia?
bacteriophage; 30 min
VSV; 6hrs
vaccinia; 24 hrs
81
Productivity of a virus is measured by ______
amplification
VSV 1:1000
Vaccinia 1:100
82
What methods rare used to initially discover viruses?
- disease in host
| - contaminant in cell culture
83
What are the methods for confirmation of a virus?
- purification of virus
-confirmation of disease
(animals,eggs, cell culture-preferred)
84
What are the principle of detection and quantification methods?
- infectivity
- physical
- genome
- serological
85
_____ methods are useful for viruses that cannot be cultivated
molecular
86
What are the 4 types of infection assays?
- infection assays
- particle assay
- genome
- serological
87
What are the 4 types of infection assays?
- cytopathic effect(CPE)
- fluorescent focus
- plaque assay
- infectious dose
88
What are the two types of particle assays?
- electron microscopy
| - hamagglutinin assay
89
What are the 2 types of genome assays?
- PCR
| - southern (DNA) & Northern (RNA)
90
What are the 3 types of serological assays?
- virus neutralization
- enzyme link immunosorbant assay (ELISA)
- Western (protein) blot
91
Different methods of virus detection and quantification give _____ answers?
different
92
How many infectious viruses do you have?
particle to PFU ranges from 1:1 to 1:10,000
93
Viruses are "alive" inside ____ only
cells
94
Human viruses have diameters of ___- ____ nm
30-300nm
95
Viruses are classified by ____, ____ ____ structure, and _____ stragegy
genome, virus particle structure, replication strategy
